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need help on constucting a helix

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need help on constucting a helix
Posted by Anonymous on Saturday, August 2, 2003 1:04 PM
I have been reading the model railroader book on bench work constructing and I am confused about construting a helix. It states, "the diameter of a helix is roughly the with of the track bed plus the width of two track radii". As you can see I'm not a math whiz. Can you explain what this means???
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need help on constucting a helix
Posted by Anonymous on Saturday, August 2, 2003 1:04 PM
I have been reading the model railroader book on bench work constructing and I am confused about construting a helix. It states, "the diameter of a helix is roughly the with of the track bed plus the width of two track radii". As you can see I'm not a math whiz. Can you explain what this means???
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Posted by Anonymous on Saturday, August 2, 2003 7:00 PM
First of all the diameter of a circle is two radius. So if you have a three foot radius, your diameter is 6 feet. Basically the formula in plain language is saying your helix needs to be a bit wider than your widest track.

So, if you have a 30 inch radius track, that is 60 inches in diameter (5 feet) so you need it to be a bit wider, I personally would add around 3 inches to the radius, to take in width for construction, etc. So your diameter would be 5 1/2 feet (or 33 inch radius).

If you build a helix, try to double track it as you can always use the second track for staging or what have you. Trains spend so much time in a helix, most double track anyway so that a train going up doesn't have to wait for a train coming down.
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Posted by Anonymous on Saturday, August 2, 2003 7:00 PM
First of all the diameter of a circle is two radius. So if you have a three foot radius, your diameter is 6 feet. Basically the formula in plain language is saying your helix needs to be a bit wider than your widest track.

So, if you have a 30 inch radius track, that is 60 inches in diameter (5 feet) so you need it to be a bit wider, I personally would add around 3 inches to the radius, to take in width for construction, etc. So your diameter would be 5 1/2 feet (or 33 inch radius).

If you build a helix, try to double track it as you can always use the second track for staging or what have you. Trains spend so much time in a helix, most double track anyway so that a train going up doesn't have to wait for a train coming down.
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Posted by Anonymous on Saturday, August 2, 2003 8:19 PM
Cassidy,

I want to add an answer to a question you did not ask. How do you determine the radius and grade of the helix? As Rick said, the diameter is twice the radius. You probably also remember the distance around the circle, the circumference, is 3.14 x diameter.

Now consider the vertical geometry problem for a minute. Depending on how you decide to build the helix, the roadbed will vary in thickness from a half-inch to an inch, possibly more. If the absolute minimum clearance over the rail you need is three inches and the roadbed is an inch thick, you should figure on four inches of grade change minimum per revolution. Since grades combined with curves produce more drag on the train than either alone, I would try and avoid going steeper than 2% even though the track in the helix is considered concealed track. So when you combine the vertical geometry with the horizontal geometry you get something like this . . .

2.5% grade . . . . . 3.5 inch rise . . . . . 22.5 inch min. radius
2.5% grade . . . . . 4.0 inch rise . . . . . 25.5 inch min. radius
2.0% grade . . . . . 3.5 inch rise . . . . . 28 inch min. radius
2.0% grade . . . . . 4.0 inch rise . . . . . 32 inch min. radius
2.0% grade . . . . . 4.5 inch rise . . . . . 36 inch min. radius

and so on. My point is that you have to remember to consider both the vertical and horizontal geometry in order to establi***he minimum radius for your helix. Good Luck - Ed
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Posted by Anonymous on Saturday, August 2, 2003 8:19 PM
Cassidy,

I want to add an answer to a question you did not ask. How do you determine the radius and grade of the helix? As Rick said, the diameter is twice the radius. You probably also remember the distance around the circle, the circumference, is 3.14 x diameter.

Now consider the vertical geometry problem for a minute. Depending on how you decide to build the helix, the roadbed will vary in thickness from a half-inch to an inch, possibly more. If the absolute minimum clearance over the rail you need is three inches and the roadbed is an inch thick, you should figure on four inches of grade change minimum per revolution. Since grades combined with curves produce more drag on the train than either alone, I would try and avoid going steeper than 2% even though the track in the helix is considered concealed track. So when you combine the vertical geometry with the horizontal geometry you get something like this . . .

2.5% grade . . . . . 3.5 inch rise . . . . . 22.5 inch min. radius
2.5% grade . . . . . 4.0 inch rise . . . . . 25.5 inch min. radius
2.0% grade . . . . . 3.5 inch rise . . . . . 28 inch min. radius
2.0% grade . . . . . 4.0 inch rise . . . . . 32 inch min. radius
2.0% grade . . . . . 4.5 inch rise . . . . . 36 inch min. radius

and so on. My point is that you have to remember to consider both the vertical and horizontal geometry in order to establi***he minimum radius for your helix. Good Luck - Ed
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Posted by Anonymous on Sunday, August 3, 2003 6:43 PM
Lynn Westcott, I believe - suggested you could use two 1/4 inch hard board laminated together, and you would have sufficient strength, but most have never tried this. He did say to seal it with a paint sealer so moisture wouldn't be a problem.

If you have two layers of laminated hard board, or plywood (that most use - I would use ply wood), then you overlap each layer so that building the circle is easy.

If I were building one - and almost all my friends have helix's on their layout - some more than one. I would use L brackets to attach the circular helix to the support poles (can't think of the proper word right now) on the inside only. So quite rightly you are thinking that the outside circles unsupported would be wobbly - and they would be.

Although normally I'm not a chicken wire kind of guy for support building mountains, I would use it on the outside of the helix, nailing it to the plywood. I then would - for the sake of speed - use plaster gauze and plaster all the chicken wire. Once the plaster gauze has set, your helix will be very solid.
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Posted by Anonymous on Sunday, August 3, 2003 6:43 PM
Lynn Westcott, I believe - suggested you could use two 1/4 inch hard board laminated together, and you would have sufficient strength, but most have never tried this. He did say to seal it with a paint sealer so moisture wouldn't be a problem.

If you have two layers of laminated hard board, or plywood (that most use - I would use ply wood), then you overlap each layer so that building the circle is easy.

If I were building one - and almost all my friends have helix's on their layout - some more than one. I would use L brackets to attach the circular helix to the support poles (can't think of the proper word right now) on the inside only. So quite rightly you are thinking that the outside circles unsupported would be wobbly - and they would be.

Although normally I'm not a chicken wire kind of guy for support building mountains, I would use it on the outside of the helix, nailing it to the plywood. I then would - for the sake of speed - use plaster gauze and plaster all the chicken wire. Once the plaster gauze has set, your helix will be very solid.
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Posted by ndbprr on Friday, August 8, 2003 2:04 PM
The way I constructed mine was to first consider the radius of the track(s). If you will have two tracks you need to take the radius of the outer track plus at least two inches ( say 34"+2"=36+ radius) for you outer edge. If your inner radius is 30" subtract 2" form it for your inner edge which =28". 36 - 28" means your baseboard will be 8" wide. You can then cut it out using a homemade circle cutter on a band saw or using a saber saw manually. The easiest part is then to drill holes in the sections and use a threaded rod and double nuts and washers to establish your grade. This is much easier than spacer blocks and allow future adjustment in the event it is needed. My helix is 48 and 50.5 inch radius which makes it 10' wide. Fortunately the space for this existed in the perfect location. This kept the grade manageable and not too much strain on the engines. Don't foreget to lay your track as you assemble the helix unless you really tiny hands and tools!
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Posted by ndbprr on Friday, August 8, 2003 2:04 PM
The way I constructed mine was to first consider the radius of the track(s). If you will have two tracks you need to take the radius of the outer track plus at least two inches ( say 34"+2"=36+ radius) for you outer edge. If your inner radius is 30" subtract 2" form it for your inner edge which =28". 36 - 28" means your baseboard will be 8" wide. You can then cut it out using a homemade circle cutter on a band saw or using a saber saw manually. The easiest part is then to drill holes in the sections and use a threaded rod and double nuts and washers to establish your grade. This is much easier than spacer blocks and allow future adjustment in the event it is needed. My helix is 48 and 50.5 inch radius which makes it 10' wide. Fortunately the space for this existed in the perfect location. This kept the grade manageable and not too much strain on the engines. Don't foreget to lay your track as you assemble the helix unless you really tiny hands and tools!
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Posted by Anonymous on Sunday, October 19, 2003 1:35 AM
Concerning laying double tracks in a helix, has anyone constructed the inner and outer tracks going in opposite directions; one going down clockwise while the other goes up clockwise? I have a 5 foot area but the entry and exit areas are limited. I assume it will require 3 threaded rod supports at each location but I'm not sure I should try it at all, although that will mean reworking the plan from scratch. I want 2 levels + hidden storage below. For rsn48, the term for the support poles is "standards" Bob T
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Posted by Anonymous on Sunday, October 19, 2003 1:35 AM
Concerning laying double tracks in a helix, has anyone constructed the inner and outer tracks going in opposite directions; one going down clockwise while the other goes up clockwise? I have a 5 foot area but the entry and exit areas are limited. I assume it will require 3 threaded rod supports at each location but I'm not sure I should try it at all, although that will mean reworking the plan from scratch. I want 2 levels + hidden storage below. For rsn48, the term for the support poles is "standards" Bob T
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Posted by Anonymous on Sunday, October 19, 2003 8:22 AM
Looks like a helix in a helix would serve your purpose. Entry and exit points would need to be carefully planned for the inside track. If you could separate the inside/outside roadbeds by half a turn, three rods may do for the supports, just watch your clearances. Good luck.
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Posted by Anonymous on Sunday, October 19, 2003 8:22 AM
Looks like a helix in a helix would serve your purpose. Entry and exit points would need to be carefully planned for the inside track. If you could separate the inside/outside roadbeds by half a turn, three rods may do for the supports, just watch your clearances. Good luck.
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Posted by Anonymous on Sunday, October 19, 2003 2:38 PM
Hey MarkGS, have you seen this done, a helix in a helix? I was planning to connect them at a couple different heights by flattening them for an inch or two. It would be a bit easier with the threaded rod. Also, the inner helix would extend lower than the outer on and they would end at the top at the same height. What do you mean by seperating the two helixes by half a turn? Thanks for the response. Bob T
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Posted by Anonymous on Sunday, October 19, 2003 2:38 PM
Hey MarkGS, have you seen this done, a helix in a helix? I was planning to connect them at a couple different heights by flattening them for an inch or two. It would be a bit easier with the threaded rod. Also, the inner helix would extend lower than the outer on and they would end at the top at the same height. What do you mean by seperating the two helixes by half a turn? Thanks for the response. Bob T
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Posted by Anonymous on Sunday, October 19, 2003 8:08 PM
Bob;

Not yet Bob. Since one goes up and one down in the double helix described, the grades wont match and the offset would allow you (hopefully) to use the same rod to support both the inside and outside helix. An oval helix may also make it easier to cross at grade at top and bottom without having to extend the inside above or below the outside helix. ( Too long a day to think this hard in 3D). Anyway, I cheat now and use the kit on the market for my helix.
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Posted by Anonymous on Sunday, October 19, 2003 8:08 PM
Bob;

Not yet Bob. Since one goes up and one down in the double helix described, the grades wont match and the offset would allow you (hopefully) to use the same rod to support both the inside and outside helix. An oval helix may also make it easier to cross at grade at top and bottom without having to extend the inside above or below the outside helix. ( Too long a day to think this hard in 3D). Anyway, I cheat now and use the kit on the market for my helix.
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Posted by dknelson on Monday, October 20, 2003 8:00 AM
Don't forget the EasyHelix sold by Trainstyles -- they advertise in MR and MRP. I have seen these set up and while they are a bit pricey (compared to what i guess is the question, as nobody else makes one) the engineering seems quite sound. At the very least it is worth getting their literature. I suspect they will be taking part in this year's Trainfest in Milwaukee (November 8-9). They did last year and the owner is happy to answer any questions.
Dave Nelson
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  • From: Milwaukee WI (Fox Point)
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Posted by dknelson on Monday, October 20, 2003 8:00 AM
Don't forget the EasyHelix sold by Trainstyles -- they advertise in MR and MRP. I have seen these set up and while they are a bit pricey (compared to what i guess is the question, as nobody else makes one) the engineering seems quite sound. At the very least it is worth getting their literature. I suspect they will be taking part in this year's Trainfest in Milwaukee (November 8-9). They did last year and the owner is happy to answer any questions.
Dave Nelson
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Posted by ndbprr on Tuesday, October 21, 2003 1:06 PM
There have to be as many ways of doing this as there are helixs out there. personally I would add the cost of threaded rods hung from the ceiling joists for a couple of reasons:
1. Double nutted it is fully adjustable at some point in the future should it need it
2. It is one H*** of a lot easier to get into the center if you need to because of problems like a derail or stalled engine.
My last railroad had a duckunder and was built when I was 32. It doesn't exist any more because I'm not 32 any more and got to be a pain. As well as the easiest to alter this way allows the most ease of entry to the center.
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Posted by ndbprr on Tuesday, October 21, 2003 1:06 PM
There have to be as many ways of doing this as there are helixs out there. personally I would add the cost of threaded rods hung from the ceiling joists for a couple of reasons:
1. Double nutted it is fully adjustable at some point in the future should it need it
2. It is one H*** of a lot easier to get into the center if you need to because of problems like a derail or stalled engine.
My last railroad had a duckunder and was built when I was 32. It doesn't exist any more because I'm not 32 any more and got to be a pain. As well as the easiest to alter this way allows the most ease of entry to the center.
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    April 2003
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Posted by Anonymous on Friday, November 14, 2003 9:52 PM
NDPBRR, that idea of hanging the helix from the ceiling is quite innovative. I think it is one I will have to give serious thought to. I had planned to construct a workbench area within the helix and this will make that easier. Thanks, Bob
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Posted by Anonymous on Friday, November 14, 2003 9:52 PM
NDPBRR, that idea of hanging the helix from the ceiling is quite innovative. I think it is one I will have to give serious thought to. I had planned to construct a workbench area within the helix and this will make that easier. Thanks, Bob

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